The present invention relates to a burst synchronization technique in time division multiple access (TDMA) communication system, especially in time division multiple access communication systems making use of stationary communication satellites.
As used herein, the term multiple access communication refers to a method in which a plurality of communication stations communicate with each other through one repeater apparatus. Such systems have been widely employed especially in the field of satellite communication. Prior art multiple access communication systems have been established according to a frequency division system, that is, a system in which frequencies to be used for communication between the respective stations are preliminarily allotted.
Recent developments in digital techniques have permitted the employment of multiple access communication on a time division basis in place of the frequency division basis. Multiple access communication on a time division basis is a method in which time slots are allotted for communication between the respective stations. Such systems are highly flexible because change of the allotment time is easy. However, in order to maintain such communication systems, various kinds of synchronizing functions are necessary. The burst synchronization according to the present invention is also directed to one of said various kinds of synchronization. Furthermore, recent advances in the field of radio communication, have made it desirable to utilize frequency bands higher than 10 GHz (e.g., quasi-millimeter wave band, millimeter wave band, . . . . . ). However, if such frequency bands are utilized for space propagation, there was a fear that they may be subjected to large attenuation caused by rainfall resulting in degradation of a C/N ratio (carrier power to noise power ratio) and thereby collapse of the synchronizing system itself. To avoid this problem, prior art systems improve the C/N ratio by increasing the number of bits in a carrier wave synchronizing signal, a bit timing synchronizing signal and a frame synchronizing signal. However, such an approach necessitates the transmission of surplus signals which are unnecessary for an inherent data transmission. Not only does this lower the transmission efficiency of the system but it limits the extent of improvement thereof.